ABSTRACT. Anchor nails are commonly used in the construction industry. They are categorized as epoxy and friction nails. Epoxy nails are stronger but they require skilled labor for installation and are expensive. For general applications mechanically installed friction nails are preferred. Till date there exists no non-destructive testing method to estimate the load carrying capacity of these nails. The study presents a newly developed non-destructive testing method to estimate load carrying capacity by relating the rebound value of Schmidt hammer to the pull-out load carrying capacity of nail. Factors affecting the rebound hammer such as hardness of the nail head, embedment length, diameter, concrete strength, the damage caused inside the concrete, nail alignment and the interfacial frictional bond are also studied. A relationship between pull-out strength and rebound value Rfor 50 and 38 mm diameter nails with embedment lengths of 10 and 20 mm is presented.

ABSTRACT . All experts have expected the rapid exhaust of the conventional energy resources. Therefore, the utilization of wind energy is very important and finds nowadays great interest. The present paper aims at enhancing the performance of wind-driven induction generators at the different expected wind speeds through controlling both the stator and rotor sides. Controlling the stator side is done via a cycloconverter, while controlling the rotor side is done through adding resistances in the rotor circuit. This is achieved by connecting a bridge rectifier feeding a single resistance shunted by a dc chopper. This enables easier electronic control.The combined-controlled induction generator has been modelled at steady-state conditions using a frequency domain equivalent circuit. A new technique has been used to determine the stator cycloconverter frequency and the value of the added resistance in the rotor of the generator to track the maximum wind-energy point. Computer programs have been developed to compare the performance characteristics of the combined-controlled induction generator (CCIG) with the uncontrolled induction generator (UCIG). The comparison have revealed that the control of the induction generator through the stator cycloconverter and the rotor added resistances has enabled capturing more energy from the wind, and delivering more power to the network.

This paper is a detailed tutorial exposition of the analysis of synchronous Boolean networks via a particular matrix product called the Semi-Tensor Product (STP) of matrices, which multiplies two matrices and in which the column dimension of the first matrix is not necessarily equal to the row dimension of the second matrix, but is possibly a multiple or divisor of it. The state space of a Boolean network of nodes is denoted herein by a vector of states in natural order obtained as the STP of 2-element vectors representing the network variables. A notable contribution of the paper is that its matrix expression of logic follows the conventional truth-table order, and not the reverse unfamiliar order followed so far by the STP community. We reproduce the STP analysis of a classical example network. We include minute details that make the STP manipulations easily accessible to and more understandable by their potential users. Our analysis points to more efficient implementations of the STP solution in which the and binary operations do not inflict a cost more than they really deserve.

ABSTRACT. This paper presents an algorithm that computes the uncertainty in the availability of power system protection using fault-tree modeling. The probability of a fault-tree top event such as "Protection Fails to Clear the Fault" is evaluated in terms of the nominal value and uncertainty of each of the basic-event probabilities. The proposed algorithm starts by obtaining the fault-tree top-event expression in the switching domain (Boolean-domain) and then converting it to an availability expression in the probability domain. The algorithm then utilizes the multiaffine nature of this reliability expression in the exact assessment of its uncertainty. An example of a typical power system protection scheme is presented wherein exact numerical estimates are obtained for both the nominal value and variance of the top-event probability.